[svawter]

I do not believe that it was specifically covered, but "Chassis & Crossbow" rules were published (first) in ADQ for low tech vehicles (basically no armor, no fancy weapons, no fancy accessories, etc.) and later in Dueltrack but I don't think it survived into 4th ed (CW Compendium/updated Deluxe CW)

Those rules can be used to run games Mad Max style (handguns only) upward to mounted .50 cal, etc., generally fired strait out the facing instead of into an arc; there were pintle mounts that allowed weapons on the roof to have a 180 arc and also ring mounts for something akin to a turret cupola style